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Old 05-20-2020, 11:28 AM   #1
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Join Date: Apr 2019
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Cummins ISL check engine

New to us 2004 Dutch Star with Cummins ISL engine is sporadically displaying the check engine. The engine sputters and loses power for a minute or two and then recovers for a while. Any ideas?

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Old 05-20-2020, 11:32 AM   #2
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Location: Pennsylvania
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I don’t know but i had a 400ISL built in 2006 on my 07 Ellipse.
I change the fuel and water separator filters every yr no matter what miles I drive Along with the oil and filter. I would guess if something wasn’t changed it could be clogged up.
My guess is the fuel filter first. The water separator has a alert for water in fuel on the dash
One more thing air filters need to be changed every 30,000 miles. That will affect your turbo for sure if it’s dirty

2020 Winnebago Horizon 42Q
Maxum Chassis, 450 ISL
99 Storm 30H, 04 Southwind 32 VS, 07 Ellipse 40FD
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Old 05-20-2020, 12:49 PM   #3
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I had a 2008 Monaco w/ Cummins ISL 400HP that would do the same thing. It was acting like a gas engine when it would miss. This would happen for a few minutes, then clear up. Road conditions didn't matter (level cruising or uphill under a load). Took it to a Cummins authorized repair center. They said it could be a short in the injector wiring harness (known issue). They checked the harness and no shorts. They removed one injector and found that the electrical connector in the injector had a crack. The connector was a small threaded stud, about 3/16" diameter. The portion that was cracked was inside the body of the injector so it didn't completely fall out. What was happening was that crack would expand and contract with engine temperature. The expansion & contraction along with the vibrations would sometimes create an open circuit and would not allow the injector to fire, causing the "missfire" and rough running. They replaced the one injector and I never had the problem again.
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Old 05-21-2020, 06:19 AM   #4
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Unit was completely serviced 150 miles ago with all filters changed so that shouldn’t be a cause, but the short in the injection harness or an injector itself is interesting. I’ll have it checked out. Thanks to both of you.
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Old 05-21-2020, 06:33 AM   #5
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I have a ISL in my rig. I had a similar problem when I filled up with B20 after not using bio-diesel for a while. Seems bio-diesel has more solvent and dissolves more of the crud at the bottom on your tank. After filling up, I was getting a miss/hesitation especially when climbing. As a temporary fix, I put some Diesel Kleen in and got home (1000 miles). Once home and replaced both fuel filters and no further problems.

Even though you've had service done recently, it's much cheaper to dump some Diesel Kleen in and replace those fuel filters as opposed to someone diagnosing your wiring harness.

Good luck!
Tom and Katharine
'07 Winnebago Tour 40TD, 400hp Cummins
'17 Winnebago View 24V, '02 R-Vision B+
RVing for 20 years & 200,000+ miles
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Old 05-21-2020, 06:39 AM   #6
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Two fuel filters cost less than one hour of tech time.
Myron & Deborah
08 HR Endeavor 40 SKQ
2012 Ford Edge Limited FWD 3.5L
Aluminator tow bar, Demco base plate
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Old 05-22-2020, 07:58 AM   #7
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Agree with your comments. I have found a common denominator though. It only happens after driving as few as 7 or 8 miles in rain. Like yesterday in AL. No rain -no problems.
Although it’s not as susceptible as a gas engine, there are still some important electrical components in there. Once I pull over and the rain passes after about 10 or 15 minutes of sitting, no problem. Going to check for faulty connections and to see what I can spray with silicone..
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Old 05-22-2020, 08:03 AM   #8
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If you have the same LBCU (Light Bar Control Unit)...you can drill down into Maintenance and retrieve the engine codes. Take a picture/write them down...then call Cummins or your Chassis Mfg. Hotline and have them decode it for you. If it's an injector problem...it will throw a code.
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